1. Field of Invention
The present invention relates to a system for controlling a chemical mechanical polishing process and a control method for the same. More particularly, the present invention relates to a control system for controlling a multi-layer chemical mechanical polishing process and a control method for the same.
2. Description of Related Art
In the semiconductor process, with the decrease of the device size, the resolution of the photolithography is increased. Furthermore, with the decrease of the depth of focus, the demand for having a more even surface of the wafer is high.
Currently, the wafer planarization is accomplished by the chemical mechanical polishing (CMP) process. Typically, the CMP process possesses the advantages including low cost, high polishing rate and high planarization efficiency. However, in the CMP process, there still exists some drawbacks. For the multilayered structure composed of the stacked-heterogeneous material layers, the physical property of each stacked-heterogeneous material layer is different from each other so that the removal rate of each stacked-heterogeneous material layer is different from each other even though the polishing rate is fixed.
Typically, in order to precisely polish away a predetermined thickness of the multilayered structure, it is necessary to measure the thickness of the topmost stacked-heterogeneous material layer, the removal rate of the topmost stacked heterogeneous material layer and then to estimate the CMP process time of the topmost stacked-heterogeneous material layer. That is, the CMP process is performed to polish away one material layer at a time. Hence, it is not easy to well control a multi-layer CMP process on a multi-layered structure for polishing away a predetermined thickness. In addition, because the CMP process is performed to polish away one material layer at a time in the multi-layer CMP process, the through put is low and the cost is high.